Spinal Surgical Implant and Related Methods

ABSTRACT

This invention relates generally to spine surgery and, in particular, to a surgical implant for separating adjacent spinal vertebrae.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/918,316 filed Mar. 12, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/823,329, filed Aug. 11, 2015, which is acontinuation of U.S. patent application Ser. No. 12/317,867 filed Dec.29, 2008, which claims the benefit of priority to U.S. ProvisionalPatent Application No. 61/009,546 filed Dec. 28, 2007, the entirecontents of which are incorporated by reference as if set forth hereinin its entirety.

BACKGROUND OF THE INVENTION I. Field of the Invention

This invention relates generally to spine surgery and, in particular, toa surgical implant for separating adjacent spinal vertebrae.

II. Discussion of the Prior Art

The spinal column is made up of individual vertebrae that providesupport for the body and allow spinal movement. Between each vertebrasits a fibrocartilaginous disc that serves as a cushion and allowsslight movement of the vertebrae. Spinal fusion procedures are commonsurgical techniques used to correct problems with displaced, damaged, ordegenerated discs due to trauma, disease, or aging. Currently estimatessuggest there are approximately 500,000 to 750,000 spinal fusionprocedures performed each year in the United States. Generally, spinalfusion procedures involve removing the diseased or damaged disc andinserting one or more intervertebral implants into the resulting discspace. Introducing the intervertebral implant restores the heightbetween adjacent vertebrae, which reduces or eliminates neuralimpingement and pain commonly associated with a damaged or diseaseddisc.

While various intervertebral implants are currently available in theprior art, there exists a need for an implant that can be inserted whensurgical angles are less than optimal due to surgical constraints, theanatomical location of the vertebrae, or when two or more fusions areperformed within one surgical corridor. When the surgical angle is lessthan optimal, the advancing implant may gouge or injure the vertebralendplate as it enters the intervertebral space. Also, it may benecessary for the surgeon to remove a portion of the side of thevertebral body to improve the entry angle into the intervertebral space.This may have the undesirable effect of destabilizing the interbodyfusion. The present invention addresses this need.

SUMMARY OF THE INVENTION

The present invention includes a spinal fusion system for performingspinal fusion between adjacent lumbar vertebrae, including an exemplaryspinal fusion implant. In one embodiment, the implant has a generallyrectangular shape, with a leading element, a trailing element. Theleading element and the trailing element are connected via flexibleelement. The flexible element allows the trailing element to moverelative to the leading element (or vice versa). Thus, trailing element(and/or leading element) may bend from a neutral position in which thetrailing element (and/or leading element) is aligned with thelongitudinal axis L to a biased position in which the trailing element(and/or the leading element) deviates from the longitudinal axis L. Thisflexibility allows the implant to adopt various temporary profiles thatmay be desirable, particularly during insertion. For example, when theoperative corridor used to access the disc space is offset or angledrelative to the plane of the disc space the implant may transition fromthe offset access trajectory to the disc space in stages (e.g. theleading element may transition before the trailing element), thusprotecting the vertebral endplates during insertion. The flexibleelement should thus be flexible enough to allow the trailing element tobend appropriately without effecting the overall integrity and strengthof the implant.

The flexible element may comprise any number of suitable formsincluding, but not limited to a spring, a textile body, and anelastomeric body. The leading element, trailing element, and flexibleelement may be formed of a single component. Alternatively, leadingelement, trailing element, and flexible element may comprise separatecomponents. It will be appreciated that any manner of mechanisms ortechniques may be used attach the flexible element to the leadingelement and trailing element. By way of example only, the flexibleelement may be attached via mechanical fasteners (e.g. snaps, rivets,screws, pins, etc. . . . ), chemical bonding, thermal bonding,adhesives, and molding.

The implant is preferably configured for lateral introduction into thedisc space. By way of example, the implant may be particularlyadvantageous for implanting positioning the implant at L5-S1 via alateral approach. By way of example only, the operative corridor may becreated using any know tissue distraction and/or tissue retractionsystems. The skin entry position depends upon individual patient anatomybut should be positioned just superior to the iliac crest. The distalend of the tissue distraction/retraction system may then be advanced atan angle towards the L5-S1 disc space, avoiding the iliac crest andthereafter opened to a final working corridor. After the creation of theoperative corridor, the intervertebral space may be prepared via anynumber of well known preparation tools, including but not limited tokerrisons, rongeurs, pituitaries, and rasps. According to oneembodiment, the preparation tools may utilize distal working endsangularly offset from the longitudinal axis of the tool shafts tofacilitate entry into the disc space through the angled operativecorridor. After preparation is complete, the implant is preferablyadvanced through the operative corridor in the neutral position (i.e.with leading element and trailing element aligned with the longitudinalaxis L and the operative corridor).

The flexible element permits the trailing element to move relative tothe leading element as the leading element enters the disc space. Inthis manner, the longitudinal axis L of the implant is permitted torotate into alignment with the disc space, despite the small height ofthe disc space relative to the length of the implant and any spaceconstraints in the operative corridor and the implant may be advancedinto the disc space without causing damage.

According to another embodiment the leading element and trailing elementare connected by an articulating element. The articulating elementallows the trailing element to move relative to the leading element (orvice versa). The articulating element may be constructed of any suitablebiocompatible material, but preferably, comprises the same material asleading element and trailing element. One articulating elementpreferably attaches to an interior surface of both sidewalls on eachside of the implant. By attaching the articulating element to theinterior surface of sidewalls the outer dimensions of implant may remainthe same. Any number of additional articulation elements within oneimplant is also contemplated. Intervening members may connect thearticulating elements with the leading and trailing ends. The additionalarticulation elements allow the implant to advance into anintervertebral space at greater and greater angles, depending on thenumber of articulation elements.

In still other embodiments, the leading element and trailing element maybe connected via wires or tethers. Additional one or more additionalelement may be situated between the leading element and the trailingelement. Various mechanisms for locking the elements together afterinsertion are also contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescriptions taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a side view of an implant having a first element and a secondelement movably connected about the longitudinal axis, according to oneembodiment of the present invention;

FIG. 2 is a side view of the implant of FIG. 1 wherein an element of theimplant is offset relative to the longitudinal axis, according to oneembodiment of the present invention;

FIG. 3 is a top view of the implant of FIG. 1, according to oneembodiment of the present invention;

FIG. 4A is a side view of the implant of FIG. 1 being inserted to anintervertebral space through an operative corridor having an axis offsetfrom the plane of the intervertebral space; according to one embodimentof the present invention;

FIG. 4B is a side view of the implant of FIG. 4A with a first elementpositioned within and aligned with the plane of the disc space and asecond element aligned with the axis of the operative corridor prior tobeing advanced into the disc space, an operative corridor having an axisoffset from the plane of the intervertebral space; according to oneembodiment of the present invention;

FIG. 5 is a side view of the implant of FIG. 4A completely inserted intoan intervertebral space, according to one embodiment of the presentinvention;

FIG. 6 is a side view of an implant having a first element and a secondelement movably connected about the longitudinal axis, according toanother embodiment of the present invention;

FIG. 6A is a cross-sectional view of the implant of FIG. 6, according toone embodiment of the present invention;

FIG. 7 is a top view of the implant in FIG. 6, according to oneembodiment of the present invention;

FIG. 8 is a top cross-sectional view of an implant having multipleelements movably connected about the longitudinal axis, according toanother embodiment of the present invention;

FIG. 9 is a top view of an implant having multiple elements movablyconnected about the longitudinal axis, according to yet anotherembodiment of the present invention;

FIG. 10 is a side view of the implant of FIG. 9, according to oneembodiment of the present invention;

FIG. 10A is a cross-sectional view of the implant of FIG. 9, accordingto one embodiment of the present invention;

FIG. 11 is a top view of the implant of FIG. 9, wherein the multipleelements are coupled in a locked position, according to one embodimentof the present invention;

FIG. 11A is a cross-sectional view of the implant of FIG. 11; accordingto one embodiment of the present invention;

FIG. 12 is a side view of the implant of FIG. 11, according to oneembodiment of the present invention;

FIG. 13 is a side view of an implant having a first element and a secondelement movably connected about the longitudinal axis, according tostill another embodiment of the present invention;

FIG. 14, is a side view of the implant of FIG. 13 wherein an element ofthe implant is offset relative to the longitudinal axis, according toone embodiment of the present invention; and

FIG. 15 is a side view of the implant of FIG. 13, wherein first andsecond elements are aligned with the longitudinal axis of the implantand are drawn tight together after positioning within an intervertebraldisc space, according to one embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Illustrative embodiments of the invention are described below for thepurposes of understanding the principles of the invention. No limitationof the scope of the invention is therefore intended. In the interest ofclarity, not all features of an actual implementation are described inthis specification. It will be appreciated that in the development ofany such actual embodiment, numerous implementation-specific decisionsmust be made to achieve the developers' specific goals, such ascompliance with system-related and business-related constraints, whichwill vary from one implementation to another. Moreover, it will beappreciated that such a development effort might be complex andtime-consuming, but would nevertheless be a routine undertaking forthose of ordinary skill in the art having the benefit of thisdisclosure. The invention disclosed herein boasts a variety of inventivefeatures and components that warrant patent protection, bothindividually and in combination.

With reference to FIG. 1-3, there is shown an example embodiment of animplant 10 for positioning within the intervertebral disc space betweenadjacent vertebral bodies of a spine. The implant 10, when deposited inthe disc space, facilitates spinal fusion and alleviates pain byrestoring the disc space to a desired height while natural bone growthoccurs through and/or past the implant 10. Over time the bone growthresults in the formation of a boney bridge between the adjacentvertebral bodies. The implant 10 is particularly adapted forintroduction into the disc space via a lateral (trans-psoas) approach tothe spine. The implant may nevertheless be introduced through any of avariety of other approaches (depending on the implant size), includingposterior, anterior, antero-lateral, and postero-lateral approaches,without departing from the scope of the present invention. The implant10 includes a longitudinal axis L, a leading element 12, a trailingelement 16, and a flexible element 14 extending along the longitudinalaxis L. The flexible element 14 is situated between the leading element12 and trailing element 16 along the longitudinal axis L and connectsthe leading element 12 with the trailing element 16.

The implant 10 may be provided in any number of sizes by varying one ormore of the implant height, width, and length. By way of example only,the implant may be provided with a length dimension ranging from 30 mmto 60 mm. By way of further example, the implant may be provided with awidth dimension ranging from 15 mm to 22 mm. By way of still furtherexample, the implant may be provided with a height dimension rangingfrom 5 mm to 20 mm. The size ranges described, by way of example only,are generally appropriate for implantation into the lumbar region of thespine. The dimensions of the implant may be altered according toproportions of the particular patient. Further variation of the implantdimensions may be implemented to produce implants generally appropriatefor implantation into either of the thoracic spine and the cervicalspine.

The leading element 12 and trailing element 16 may be of bone ornon-bone construction. By way of example, the leading element 12 andtrailing element 16 may be cut and shaped from a suitable allograftbone. Preferably, the allograft source comprises a donor femur, however,it will be appreciated that any suitable bone may be used.Alternatively, the leading element 12 and trailing element 16 may becomprised of any suitable bio-compatible material including, but notlimited to, polymer compositions (e.g. poly-ether-ether-ketone (PEEK)and/or poly-ether-ketone-ketone (PEKK) or any combination of PEEK andPEKK), and metals (e.g. titanium).

The leading element 12 has a top surface 18, a bottom surface 20,opposing sidewalls 22 (which comprise an anterior side and a posteriorside when the implant is positioned in the disc space), a distal end 24,and a proximal end 26. The trailing element 16 has a top surface 28, abottom surface 30, opposing sidewalls 32 (which comprise an anteriorside and a posterior side when the implant is positioned in the discspace), a distal end 34, and a proximal end 36. Though not shown, itwill be appreciated that the opposing side walls 22, 32 may bedimensioned with differing heights in order to promote the naturalcurvature of the spine. That is, by way of example, the sidewalls 22, 32may be dimensioned such that the sidewalls comprising the anterior sidewhen the implant is positioned in the disc space have a greater heightthan the sidewalls comprising the posterior side, thus restoring thelordotic curvature of the lumbar (and cervical) spine. Alternatively,the sidewalls 22, 32 may be dimensioned such that the sidewallscomprising the anterior side when the implant is positioned in the discspace have a lesser height than the sidewalls comprising the posteriorside, thus restoring the kyphotic curvature of the thoracic spine. Thetop surfaces 18, 28 and bottom surfaces 20, 30 may be provided in anynumber of suitable surface contours, including but not limited togenerally planar, concave, and/or convex.

The leading element 12 and/or trailing element 16 may also includeanti-migration features designed to increase the friction between theimplant 10 and the adjacent contacting surfaces of the vertebral bodies.Such anti-migration features may include ridges or teeth 38 providedalong the top surfaces 18, 28 and/or bottom surface 20, 30. Additionalanti-migration features may also include one or more spike elements 40disposed at various locations along the implant 10. In one embodiment,the implant 10 includes a total of 4 spike elements 40 extending throughthe upper surfaces 18, 28 and the lower surfaces 20, 30. Spike elements40 may be positioned near the “corners” of the implant 10 where thedistal end 24 of leading element 12 meets sidewalls 22 and the proximalend 36 of trailing element 16 meets sidewalls 32. The spike elements 40may be manufactured from any of a variety of suitable materials,including but not limited to a metal, ceramic, and/or polymer material,preferably having radiopaque characteristics. The spike elements 40 mayalso take any of a variety of suitable shapes, including but not limitedto a generally elongated element disposed within the implant 10 suchthat the ends thereof extend generally perpendicularly from the upper18, 28 and/or lower surfaces 20, 30. When the spike elements 40 areprovided having radiodense characteristics and the leading and trailingelements 12, 16 are manufactured from a radiolucent material (such as,by way of example only, PEEK and/or PEKK), the spike elements 40 will bereadily observable under X-ray or fluoroscopy such that a surgeon maytrack the progress of the implant 10 during implantation and/or theplacement of the implant 10 after implantation.

The implant 10 may be configured with one or more fusion apertures 42.Preferably, each of leading element 12 and trailing element 16 include afusion aperture 42 extending in a vertical fashion through the topsurface 18, 28 and bottom surface 20, 30, respectively. The fusionapertures 42 function primarily as an avenue for bony fusion betweenadjacent vertebrae. The fusion apertures 42 may be provided in any of avariety of suitable shapes, including but not limited to the generallyrectangular shape best viewed in FIG. 3, or a generally circular, oblongand/or triangular shape or any combination thereof. The spinal fusionimplant 10 may have a plurality of visualization apertures 44 whichallow a clinician to make visual observations of the degree of bonyfusion un-obscured by the sidewalls 22, 32 of the implant 10 tofacilitate further diagnosis and treatment. Preferably, each of leadingelement 12 and trailing element 16 include at least one visualizationaperture 44. Visualization apertures may be provided in any of a varietyof suitable shapes, including but not limited to the generally oblongshape best viewed in FIGS. 1-2, or a generally circular, rectangularand/or triangular shape or any combination thereof.

Fusion between the adjacent vertebrae may be facilitated or augmented byintroducing or positioning various osteoinductive materials within thefusion apertures 42 and/or adjacent to the spinal fusion implant 10.Such osteoinductive materials may be introduced before, during, or afterthe insertion of the implant 10, and may include (but are notnecessarily limited to) autologous bone harvested from the patientreceiving the spinal fusion implant 10, bone allograft, bone xenograft,any number of non-bone implants (e.g. ceramic, metallic, polymer), bonemorphogenic protein, and bio-resorbable compositions, including but notlimited to any of a variety of poly (D,L-lactide-co-glycolide) basedpolymers.

The leading element 12 and the trailing element 14 are connected viaflexible element 14. Flexible element 14 allows the trailing element 16to move relative to the leading element 12 (or vice versa). Thus,trailing element 16 (and/or leading element 12) may bend from a neutralposition in which the trailing element 16 (and/or leading element 12) isaligned with the longitudinal axis L to a biased position in which thetrailing element (and/or the leading element 12) deviates from thelongitudinal axis L by and angle a. This flexibility allows the implant10 to adopt various temporary profiles that may be desirable. By way ofexample, when the operative corridor used to access the disc space isoffset or angled relative to the plane of the disc space (due to, forexample, one or more anatomical and procedural constraints orconsiderations) the implant 10 may transition from the offset accesstrajectory to the disc space in stages (e.g. the leading element 12 maytransition before the trailing element 16), thus protecting thevertebral endplates during insertion. The flexible element 14 shouldthus be flexible enough to allow the trailing element 16 to bendappropriately without effecting the overall integrity and strength ofthe implant 10.

The flexible element 14 may comprise any number of suitable forms forproviding the desired flexibility to the implant 10. By way of example,flexible element 14 may comprise any one or a combination of, but notlimited to a spring, a textile body (constructed, for example, via oneor more of embroidery, weaving, three-dimensional weaving, knitting,three-dimensional knitting, injection molding, compression molding,cutting woven or knitted fabrics, etc.), and an elastomeric body.According to one embodiment, leading element 12, trailing element 16,and flexible element 14 may be formed of a single component. Accordingto one example of such an embodiment, the entire implant 10 may beformed of polymer material (e.g. PEEK) and a central portion of thecomponent may be machined in a manner that provides the necessaryflexibility. Alternatively, leading element 12, trailing element 16, andflexible element 14 may comprise separate components. It will beappreciated that any manner of mechanisms or techniques may be usedattach the flexible element 14 to the proximal end 26 of leading element12 and distal end 34 of trailing element 16, respectively. By way ofexample only, flexible element 14 may be attached via mechanicalfasteners (e.g. snaps, rivets, screws, pins, etc. . . . ), chemicalbonding, thermal bonding, adhesives, and molding.

As mentioned above, the implant 10 is configured for lateralintroduction into the disc space. A lateral approach to the disc spacecan be highly advantageous over other approaches to the spine. However,the iliac crest of the pelvis generally lies lateral to the L5-S1 discspace making a lateral approach to this spinal level (and thus theadvantages that accompany a lateral approach) difficult to achieve inpractice. According to one clinical utilization, set forth by way ofexample only, the implant 10 may be employed to advantageously accessand fuse the L5-S1 disc space from a lateral approach, as will now bedescribed. With the patient properly situated on the surgical table(preferably in the lateral decubitus position) an operative corridor iscreated to the L5-S1 disc space from a skin entry position locatedsuperior to L5-S1. By way of example only, the operative corridor may becreated using any know tissue distraction and/or tissue retractionsystems 46, such as, by way of example only, the tissue distraction andretraction assemblies shown and described in the commonly owned U.S.Pat. No. 7,207,949, the entire contents of which is incorporated byreference into this disclosure as if set forth fully herein. The skinentry position depends upon individual patient anatomy but should bepositioned just superior to the iliac crest. The distal end of thetissue distraction/retraction system 46 may then be advanced at an angletowards the L5-S1 disc space, avoiding the iliac crest. Once thedistraction/retraction system 46 reaches the L5-S1 disc space, theoperative corridor may be expanded by spreading thedistraction/retraction system 46 to a final working configuration.Alternatively, the distraction/retraction assembly may be advancedstraight to the spine from the skin entry position, and thereafteradjusted to position the distal end of the distraction/retraction system(and thus the operative corridor) adjacent to the L5-S1 disc space.

After the creation of the operative corridor, the intervertebral spacemay be prepared via any number of well known preparation tools,including but not limited to kerrisons, rongeurs, pituitaries, andrasps. According to one embodiment, the preparation tools may utilizedistal working ends angularly offset from the longitudinal axis of thetool shafts to facilitate entry into the disc space through the angledoperative corridor. After preparation, an insertion instrument 48 isutilized to advance the implant 10 through the operative corridor andinto the intervertebral space. As illustrated in FIG. 4A, the implant 10is preferably advanced through the operative corridor in the neutralposition (i.e. with leading element 12 and trailing element 16 alignedwith the longitudinal axis L).

As illustrated in FIG. 4B, the flexible element 14 permits the trailingelement 16 to move relative to the leading element 12 as the leadingelement 12 enters the disc space. In this manner, the longitudinal axisL of the implant is permitted to rotate into alignment with the discspace, despite the small height of the disc space relative to the lengthof the implant and any space constraints in the operative corridor. Theimplant 10 may thus be advance into the disc with a reduced risk ofgouging or otherwise injuring the vertebral endplates and withoutrequiring a portion of the vertebral body be removed to improve theentry angle into the intervertebral space. The insertion instrument 48may utilize any number of suitable means for engaging the trailingelement 16 of implant 10. To facilitate insertion of the implant 10, theinsertion instrument 48 may utilize an angularly offset distal headand/or a flexible shaft. Once the entire implant 10 is inserted into theprepared space and resumes a generally neutral position, the implant 10is released from the insertion instrument 48, the tissuedistraction/retraction system 46 removed, and the operative corridorclosed, as depicted in FIG. 5. As previously mentioned, additionalmaterials may be included in the procedure before, during or after theinsertion of the spinal fusion implant 10 to aid the natural fusion ofthe targeted spinal level.

Alternative example embodiments of implants capable of insertion intothe L5-S1 disc space via a lateral surgical approach as described above,are illustrated, by way of example only, in FIGS. 6-13. The alternateembodiments illustrated by way of example, in FIGS. 6-13 are similar tothe implant 10 such that repeat discussion of common elements isunnecessary and common elements are numbered accordingly. With referenceto FIGS. 6-8, implant 110 includes leading element 12 and trailingelement 16. Rather than the flexible member 14 of implant 10, however,the leading element 12 and trailing element 16 are connected by anarticulating element 50. The articulating element 50 allows the trailingelement 16 to move relative to the leading element 12 (or vice versa).Thus, trailing element 16 (and/or leading element 12) may bend from theneutral position in which the trailing element 16 (and/or leadingelement 12) is aligned with the longitudinal axis L to a biased positionin which the trailing element (and/or the leading element 12) deviatesfrom the longitudinal axis L. Implant 110 may thus adopt varioustemporary profiles prior to and during insertion into the disc space.The articulating element 50 may be constructed of any suitablebiocompatible material, but preferably, comprises the same material asleading element 12 and trailing element 16. As illustrated, onearticulating element 50 preferably attaches to an interior surface ofboth sidewalls 22 and 32 on each side of the implant. By attaching thearticulating element 50 to the interior surface of sidewalls 22, 32 theouter dimensions of implant 110 may remain the same or similar toimplant 10, however, it will be appreciated that the articulatingelement 50 may also be attached along the outer surface of sidewalls 22,32.

As best viewed in FIG. 6A, articulating elements 50 are attached to theleading element 12 and trailing element 16 with fasteners 52. In theillustrated embodiment, fasteners 52 comprise cylindrical pins insertedthrough both the articulating element 50 and the leading element 12 ortrailing element 16. Alternatively, it will be appreciated thatfasteners 52 may comprise any suitable connector, such as, for example,a post extending from articulating element 50 into a correspondingaperture on leading element 12 or trailing element 16, or vice versa.FIG. 8 is a cross-sectional view of an implant 210 according to anotherexample embodiment. Implant 210 is identical to implant 110 except thatthe length of at least one of the leading element 12 and trailingelement 16 is shortened and at least one intervening member 54 issituated between leading element 12 and trailing element 16 on each sideof the implant 210. As shown, the implant 210 includes three interveningmembers 54 on each side. For each intervening member 54 added to implant210 an additional articulating element 50 is also added. Thus, theimplant 210 as pictured utilizes four articulating elements 50 on eachside of the implant. Decreasing the length of the leading element 12 andtrailing element 16 and adding articulating elements 50 and interveningmembers 54 increases the overall offset angle (of the surgical corridorrelative to the plane of the disc space) from which the implant 210 maybe safely implanted into the disc space.

Turning now to FIGS. 9-12, an example implant 310 is illustrated.Implant 310 includes a leading element 12, a trailing element 16, and acentral element 56. Central element 56 includes a top surface 58, abottom surface 60, opposing sidewalls 62 (which comprise an anteriorside and a posterior side when the implant 310 is positioned in the discspace), a distal end 64, and a proximal end 66. The leading element 12,trailing element 16, and central element 56 are loosely connected in aninitial position via at least one wire 68 (and preferably, at least twowires 68 are utilized, as depicted herein) fixed to leading element 12and passing through central element 56 and trailing element 16, exitingfrom the proximal end 36 of trailing element 16. The wires 68 may beformed of any suitable material having flexibility enough to allowcentral element 56 and trailing element 16 to move relative to leadingelement 12 and each other. Preferably, wire 68 will also provide enoughstiffness so that movement between the elements is controlled and notfloppy. This controlled movement facilitates initial placement of theleading element 12 within the disc space. By way of example only, thewires 68 may be formed of nitanol or other similar metals. The leading,central, and trailing elements 12, 56, and 16 are further configured tointerlock with one another upon final insertion of the implant 310within the disc space. To accomplish this, central element 56 includes amale snap connector 70 extending from proximal end 66 and a female snapreceptacle 72 formed within distal end 64. Extending from proximal end26, leading element 12 includes a male snap connector 74 complementaryto the female snap receptacle 72 of central element 56. Trailing element16 includes a female snap receptacle 76 within distal end 34.

To insert the implant 310, an operative corridor is created as describedabove. After the leading end 12 is directed to the disc space, theimplant advanced all the way into the disc space with the aid of aninsertion instrument. Similar to the implants described above, theflexible nature of the wires 68 allows the implant 310 to transitionfrom the offset operative corridor into alignment with the disc space instages. After the implant is completely advanced into the disc space,the wires 68, which are fixed to leading element 12 may be pulled awayfrom the disc space while pressure is applied to the trailing element 16in a direction towards the disc space. This combined action draws theleading element and central element together, such that snap connector74 engages in snap receptacle 72, locking the leading element 12 andcentral element 56 together. The central element 56 and trailing element16 will also be drawn together such the snap connector 70 engages insnap receptacle 76, locking central element 56 and trailing element 16together. Once the implant 310 is locked together within the disc space,the wires 68 extending from trailing element 16 may be removed. This maybe accomplished, for example, simply by cutting the exposed portion ofwires 68, or any number of other suitable methods. FIGS. 9-10 illustratethe implant 310 prior to locking the leading element 12, central element56, and trailing element 16 together, while FIGS. 11-12 depict theimplant in its final locked position.

FIGS. 13-15 depict yet another example embodiment of an implant 410according to the present invention. Implant 410 comprises leadingelement 12 and trailing element 16. Leading element 12 and a trailingelement 16 are loosely connected by an embroidered tether 78 fixed toleading element 12 and passing through trailing element 16. It will beappreciated that any number of suitable tethers other than theembroidered tether described may be utilized. By way of example only,the tether may be comprised of wire similar to wires 68 described above.The proximal side 26 of leading element 12 and distal side 34 oftrailing element 16 are configured with complementary articulatingsurfaces 80 and 82, respectively. By way of example, articulatingsurface 80 of leading element 12 comprises a convex extension ofsidewalls 22 while the articulating surface 82 of trailing element 16comprises a concave depression in sidewalls 32. Alternatively,articulating surface 80 could be a concave depression and articulatingsurface 82 could be a convex extension. The complementary articulatingsurfaces 80, 82, together with the loose connection provided by tether78 permit the leading element 12 and trailing element 16 to moverelative to each other, and again, like the implants described above,allows implant 410 to transition from alignment in an operative corridorto alignment with the disc space in stages when the disc space isangularly offset form the operative corridor. To deliver implant 410through the offset operative corridor, the leading end 12 is advancedthrough the corridor until reaching the disc space. The orientation ofthe leading element is transitioned into alignment with the disc spaceand leading element 12 is positioned therein. Initially, the leadingimplant 410 may be held slightly rigid to facilitate initial positioningof the leading element 12 in the disc space by pulling tether 78 andapplying pressure to trailing element 16 with the aid of an insertioninstrument. Thereafter, providing slack to the tether 78 allows thetrailing element 16 to move relative to the leading element 12 such thatthe implant can again align with the disc space in stages. After theimplant is fully positioned within the disc space, the tether 78 mayagain be pulled while providing force in the opposite direction with theinsertion tool. This draws the leading element 12 and trailing element16 tightly together and the tether 78 may be tied or otherwise fixed atthe proximal end 36 of trailing element 16 to maintain the elements 12,16 in snug configuration. The excess tether 78 may be removed.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the invention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined herein. By way of example only,the description illustrates the use and implantation of implants intothe L5-S1 disc space via a lateral approach. It will be appreciatedhowever, that numerous situations may arise where it is desirable todeliver an intervertebral implant through an operative corridor alignedobliquely to the disc space, and the invention is not intended to belimited to the L5-S1 disc space.

1. An implant for positioning within the intervertebral disc spacebetween a pair of adjacent vertebral bodies, the implant having alongitudinal axis extending from a first end of said implant to a secondend of said implant, the longitudinal axis lying in a first plane thatseparates an upper surface and lower surface of the implant and extendsthrough the first end, second end, and opposing sidewalls of theimplant, the longitudinal axis being orthogonal to a second plane thatseparates the first end and the second end and extends through the uppersurface, lower surface, and opposing sidewalls of the implant, saidimplant comprising: a first element including the first end of theimplant and a second element including the second end of the implant,the first element and second element movable relative to one anotherabout the second plane such that at least one of said first element andsaid second element is moveable between an inline position that isaligned with the first plane and an offset position that is angularlyoffset from the first plane, the first element connected to the secondelement by at least one of a wire and a tether.